1. Technical Field
The present disclosure relates to an electro-optic modulator having a ridge waveguide structure, wherein the electro-optic modulator can achieve a high extinction ratio when functioning as an optical switch.
2. Description of Related Art
Electro-optic modulators, such as Mach-Zehner electro-optic modulators, change a refractive index of a branch (hereinafter “the first sub-branch”) of a Y-shaped waveguide by employing a modulating electric field, which utilizes the electro-optic effect. Thus, the modulator can alter a phase of light waves traversing the first sub-branch. As a result, the phase of light waves traversing the first sub-branch can be shifted and thus interfere with light waves traversing another branch (hereinafter “the third sub-branch”) of the Y-shaped waveguide. An output of the Y-shaped waveguide is modulated as the power output depending on the phase shift, which in turn depends on the modulating electric field. However, due to manufacturing imprecision inherent in an electro-optic modulator, the properties of the light waves respectively traversing the first and third sub-branches are not equal to each other. As such, when the electro-optic modulator is used as an optical switch, the power output is often larger than zero in an off state, or is less than a desired maximum value in an on state That is, an extinction ratio of the optical switch may be less than what is considered to be satisfactory.
Therefore, it is desirable to provide an electro-optic modulator that can overcome the above-mentioned problems.